1. Field of the Invention
The present invention relates to medical techniques, in particular, to apparatus and methods used to prevent an aorta rupture by means of grafts or stent-grafts. More particularly, the present invention relates to methods and apparatus for securing intravascular devices, such as grafts or stent-grafts, to the walls of blood vessels in direction from the inside of these vessels towards their outer surface.
2. Description of Related Art
An aortic aneurysm (or its rupture) is a most common form of arterial aneurysms. It is a very common type of deteriorating disease affecting the ability of a lumen to conduct fluids and may be life threatening. The aortic aneurysm is a ballooning of the wall of an artery resulting from the weakening of the artery's wall due to disease or other conditions. Left untreated, the aneurysm will frequently rupture, resulting in loss of blood through the rupture, the condition, which often leads to death.
The aorta is the main artery, which supplies blood to the circulatory system. The aorta arises from the left ventricle of the heart, passes upwards and bends over behind the heart, and passes down through the thorax and abdomen. Among other arterial vessels branching off the aorta along its path, the abdominal aorta supplies two side vessels to the kidneys, the renal arteries. Below the level of the renal arteries, the abdominal aorta continues to about the level of the fourth lumbar vertabrae (or the navel), where it divides into the iliac arteries. The iliac arteries, in turn, supply blood to the lower extremities and perineal region.
It is common for an aortic aneurysm to occur in that portion of the abdominal region between the renal arteries and the iliac arteries. This portion of the abdominal aorta is particularly susceptible to weakening, resulting in an aortic aneurysm. Such an aneurysm is often located near the iliac arteries. An aortic aneurysm larger than about five centimeter in diameter in this section of the aorta is ominous. Left untreated, the aneurysm may rupture, resulting in rapid, and usually fatal, hemorrhaging. Typically, a surgical procedure is not performed on aneurysms smaller than five centimeters because no statistical benefit exists in performing such procedures.
Aneurysms in the abdominal aorta are associated with a particularly high mortality rate; accordingly, current medical standards call for urgent operative repair. Abdominal surgery, however, results in substantial stress to the body. Although the mortality rate for an aortic aneurysm is extremely high, there is also considerable mortality and morbidity associated with open surgical intervention to repair an aortic aneurysm. This intervention involves penetrating the abdominal wall to the location of the aneurysm to reinforce or replace the diseased section of the aortic aneurysm. A prosthetic device, typically a synthetic tube graft, is used for this purpose. The graft serves to exclude the aneurysm from the circulatory system, thus relieving pressure and stress on the weakened section of the aorta at the aneurysm.
Besides synthetic grafts, there are developed and widely used all over the world particularly to prevent the rupture of aorta wall intravascular devices of the “stent-graft” type. They are inserted and located similarly to stents. The fixation of a stent-graft on the aorta walls is performed due to resilient forces of the material of the stent-graft itself usually having elastic members which bear up against the blood vessel wall or hook thereto. If the forces of resilient or elastic members of the stent-graft are insufficient for its fixation in a blood vessel, the stent-graft may be displaced from a given position and moved along the aorta due to the blood flow and peristelsic oscillations of the walls of this blood vessel, which is very dangerous to the patient.
Repair of an aortic aneurysm by surgical means is a major operative procedure. Substantial morbidity accompanies the procedure, resulting in a protracted recovery period. Further, the procedure entails a substantial risk of mortality. While surgical intervention may be indicated and the surgery carries attendant risk, certain patients may not be able to tolerate the stress of intra-abdominal surgery. It is, therefore, desirable to reduce the mortality and morbidity associated with intra-abdominal surgical intervention.
In recent years, the common repair means is to deploy a stent-graft within the lumen of the affected aorta in the region of the aneurysm. These methods and devices have been developed to attempt to treat an aortic aneurysm without the attendant risks of intra-abdominal surgical intervention. Among them are inventions disclosed and claimed in Parodi, Juan C. et al., WO 010487A1 for Graft Device for Treating Abdominal Aortic Aneurysms and its patent family, including U.S. Pat. Nos. 5,219,355, 5,522,880, 5,571,171, 5,643,208, 5,683,452, 5,693,087, 6,102,942, EP 461791A1, EP 809980A3, EP 903118A2, EP 903119A3, EP 903120A3 etc.
Parodi discloses a stent-graft device for locating inside an aorta affected by an aneurysm causing the aorta to have an inner diameter smaller than the sum of inner diameters of the iliac arteries. The graft has an upper main tubular portion dividing into two pending graft limbs capable of accommodating together within the restricted inner diameter of the aorta without the restriction of the aorta affecting the diameter of the limbs. The limbs have respective distal end portion with diameters larger than the diameters of the graft limbs so as to be accommodated and retained within the iliac arteries. Parodi's stent-graft is inserted using a tubular device also disclosed in his patent.
In other Parodi's patents there are disclosed stent-graft designs having a metal wire frame collapsible to a minimal size sufficient to insert the stent-graft into the artery through a puncture in its wall and expandable inside the aorta to a required size under the action of a radial force, such as a balloon. This frame is covered by a sheath which can contract and expand together with the frame under the action of external forces. Aforesaid stent-grafts are provided with means for mechanical fixation to the walls of the aorta or iliac arteries. Among those means we find balloon cuffs of a special shape at the stent-graft ends, see WO 010487A1, U.S. Pat. Nos. 5,522,880, 5,219,355, various hooks, elements shaped as scales, spirals and similar elements designed for fixation on the wall of the aorta or artery, see U.S. Pat. No. 5,911,733 Endovascular Expander of a Non-migrant Positioning, EP 948945A2 Endovascular Prosthesis with Fixation Means.
The problem of fixation of stents and stent-grafts inside the aorta and iliac arteries is PARTIALLY solved by other inventors likewise.
Lindenberg, Josef in EP 711135A1 discloses a stent with an improved anchorage in a vessel. The stent can be expanded from a radially contracted insertion state into a radially expanded positioning state such that in the radially expanded state at least one end has a larger radial extension than the remaining main body of the stent.
Samuels in U.S. Pat. No. 5,423,851 discloses a method and apparatus for affixing an endoluminal device to the walls of tubular structures within the body which utilizes incremental inflation of a balloon cuff to deploy radially projecting barbs attached to the cuff within a plurality of recesses.
Kugler, Chad disclose in their patent WO 19943A1 a stent-graft comprising radially expandable portions attached to one another and anchored to the aorta walls by a radial force. This stent-graft can bend to match the aorta longitudinal section by relative angular displacement of its portions.
Houser, Russel in WO 15144A1 discloses a system and components for treating aortic aneurysms including a reinforcing graft and combinations of fittings and rings for securing the graft to a host vessel, to branch vessels, for example, the iliac and renal arteries.
Edwin, Tarun et al., discloses in EP 868154A1 a structurally supported graft having a support structure with strain relief sections containing an internal surface, an external surface, or a wall thickness of a tubular graft member. The structural support forms a spiral about the tubular graft.
Numerous suggestions of stent-graft inventors present various hooks and anchor members, integral or not integral with the stent-graft frame to fixate the latter inside the aorta or iliac arteries. Such suggestions are disclosed in U.S. Pat. No. 6,015,431, EP 747020A2, EP 701800A1, EP 657147 A2, EP 466518A2, U.S. Pat. Nos. 5,669,936, 6,004,347, 5,733,325, 5,104,399, 6,030,413.
All the above-mentioned inventions have, in our opinion, a common drawback, which consists in the fact that the stent-grafts fixation on the inner walls of the aorta and iliac arteries is not reliable enough and brings to many complications. Therefore, under the action of blood flow and peristaltic oscillations of artery walls, stent-grafts are displaced from their proper positions, which may have grave consequences for the patient and result in his death because of the aorta rupture.